A method for fabricating an electrode unit which is used in a flat type image display apparatus

Abstract: The invention relates to the following method steps for fabricating an electrode unit (7) which is used in a flat type image display apparatus and consists of a plurality of flat-sheet-shaped electrodes: Mounting in position a first electrode (e.g., 7f) on a second electrode (e.g., 7g) via an insulative bonding material (8); temporarily fixing said first electrode (7f) to said second electrode (7g) via a pair of opposing fixing portions each of temporary fixing parts (207f, 207g) formed in each of said first electrode (7f) and said second electrode (7g) with the bend of elastic portions each of said temporary fixing parts; permanently fixing said first electrode (7f) to said second electrode (7g) via said insulative bonding material (8); and removing said temporary fixing parts (207f, 207g).

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION The present invention relates to a fabrication method of a flat type image display apparatus which is mainly used for a TV set or a visual display terminal for computers. 2. DESCRIPTION OF THE RELATED ART In a known flat type image display apparatus, an electron beam emitted from an electron beam source is controlled (i.e., focussed, modulated and deflected) by a flat sheet-shaped electrode unit. This flat sheet-shaped electrode unit consists of plural electron beam control electrodes which are formed into a lamination body. After steps of focussing, modulating and deflection, the electron beam reaches a phosphor screen. The phosphor screen thereby emits light and forms an image thereon. FIG.15 is an exploded perspective view showing general construction of the conventional flat type image display apparatus 101. The image display apparatus 101 has a vacuum case constituted by a front panel 103, a rear panel 104 and a side wall part (not shown). A phosphor screen 102 is formed on an inner face of the front panel 103. An inbetween space defined by the front panel 103, the side wall part and the rear panel 104 is kept vacuum. A back electrode 105, plural linear cathodes 106 and a flat-shaped electrode unit 107 are provided from the back panel 104 toward the front panel 103. The linear cathodes 106 act as an electron beam source. The back electrode 105 is formed on an inner face of the back panel 104. The electrode unit 107 consists of an electron beam extracting electrode 107a, a modulation electrode 107b, a vertical focussing electrode 107c, a horizontal focussing electrode 107d, a horizontal deflection electrode 107e, a shield electrode 107f and a vertical deflection electrode 107g. Electron beams emitted from the linear cathode 106 pass through the electron beam extracting electrode 107a, the modulation electrode 107b, the vertical focussing electrode 107c, the horizontal focussing electrode 107d, the horizontal deflection electrode 107e, the shield electrode 107f and the vertical deflection electrode 107g, thereby getting focussed, modulated and deflected. Finally, a stream of the electron beams reaches a predetermined position on the phosphor screen 102, and thereby the screen emits light to make an image. In the electrode unit 107, the respective electrodes 107a --- 107g are bonded with each other with each predetermined gap held therebetween, and they are electrically insulated from each other. As an example, a method for bonding the shield electrode 107f and the vertical deflection electrode 107g will be described with reference to FIG.16. The shield electrode 107f and the vertical deflection electrode 107g are bonded with each other with insulation therebetween held by insulative bonding members 108. Each of the insulative bonding members 108 includes a pair of bonding glass members 108a and a spacer glass member 108b for securing a predetermined gap between the electrodes 107f and 107g. A melting temperature of the spacer glass member 108b is higher than that of the bonding glass member 108a. A substrate 109 and a stamper 110 constitute an electrode bonding tool by a baking process. The substrate 109 has plural positioning pins 111 for disposing the respective electrodes 107f and 107g in position. A metal sheet 112a, which is for mainly protecting the electrode 107g, is provided between the electrode 107g and the substrate 109, and a metal sheet 112b for mainly protecting the electrode 107f is provided between the electrode 107f and the stamper 110. After disposing the metal sheet 112a on the substrate 109, the vertical deflection electrode 107g is mounted on the metal sheet 112a with the pins 111 passing through positioning holes 107ga of the electrode 107g. The vertical deflection electrode 107g is thus disposed on the metal sheet 112a. Next, the insulative bonding members 108 are put on respective predetermined positions of the vertical deflection electrode 107g. The shield electrode 107f is disposed on the insulative bonding members 108 with the pins 111 passing through the positioning hole 107f. After disposing the metal sheet 112b on the shield electrode 107f, the stamper 110 is disposed on the metal sheet 112b. The above-mentioned assembly is heated in a baking oven at the temperature of 450 °C to 500 °C, thereby melting and crystallizing the bonding glass members 108a. Thus, the shield electrode 107f and the vertical deflection electrode 107g are bonded with each other with their insulation held from each other. In a similar way to the above, the horizontal focussing electrode 107d and the horizontal deflection electrode 107e are bonded with each other, keeping a state that they are insulated from each other. Further, the modulation electrode 107b and the vertical focussing electrode 107c are bonded with each other, keeping a state that they are insulated from each other. Finally, the above-mentioned three bonded units and the electron beam extracting electrode 107a are bonded with each other with respective insulation held from each other, thus completing fabrication of the electrode unit 107. In the above-mentioned conventional construction of the flat type image display apparatus, it is very delicate to precisely locate the respective electrodes, which constitute the electrode unit 107, in position. It is actually impossible to make such a precise positioning of the respective electrode since an accuracy of the positioning is dependent on an uncertain engaging accuracy between the positioning pin 111 and the positioning hole 107fa or 107ga. To obtain a fine accuracy of the positioning, it is required to produce the positioning pin 111 and the positioning holes 107fa, 107fg with very high accuracy. However, such a very high working accuracy is incompatible with the mass production. The use of temporary fixing parts ('Fixierlappen') for bonding two flat-shaped electrodes of a flat image display apparatus via an insulating bonding material is disclosed in Feinwerktechnik + Messtechnik, vol. 99, No 7/8, August 1991, pages 335-338; M. Neusch et al. : 'Metallsteuerscheiben - eine neve Technologie'. OBJECT AND SUMMARY OF THE INVENTION An object of the present invention is to offer by fabricating a flat type image display apparatus in which plural electrodes can be positioned with very fine accuracy without spoiling the mass-productivity. In order to achieve the above object, the method of claim 1 is provided. In order to achieve the above-mentioned object, furthermore a flat type image display apparatus of the present invention comprises: a vacuum case which defines a vacuum space between a front panel having a phosphor screen on an inner face thereof and a rear panel; a plurality of linear cathodes mounted in the vacuum case; and an electrode unit mounted in tile vacuum case and including a plurality of flat-shaped electrodes bonded with and insulated from each other, the flat-shaped electrodes each having a plurality of identification holes, a relative positional relationship of the identification holes being uniform with regard to every flat-shaped electrode, positions of the identification holes being shifted in a predetermined direction from those of adjacent flat-shaped electrodes. While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is an exploded perspective view showing a flat type image display apparatus used in the method of the present invention; FIG.2 is a plan view showing seven sheets of the electrodes used in the method of the present invention; FIG.3 is a plan view showing only corner parts of the seven electrodes shown in FIG.2; FIG.4 is a plan view showing seven electrodes piled up in an order shown in FIG.3; FIG.5 is a cross-sectional view showing an identification hole shown in FIGs.2, 3 and 4; FIG.6 is a plan view showing a detail of a temporary fixing part in the present invention; FIG.7 is a side view showing a bonding process of a shield electrode 7f and a vertical deflection electrode 7g in the present invention; FIG.8 is a perspective view showing a main part including a temporary fixing parts 207f and 207g in the present invention; FIG.9 is a side view seen from "A" in FIG.8 before a bonding process; FIG.10 is a side view seen from "A" in FIG.8 after the bonding process; FIG.11 is a cross-sectional view showing seven electrodes taken on line XI - XI in FIG.4; FIG.12 is a cross-sectional view showing another configuration of an identification hole and sight holes in the present invention; FIG.13 is a plan view showing another configuration of identification holes and sight holes in the present invention when seven electrodes are superimposed; FIG.14 is a plan view showing the other configuration of identification holes and sight holes in the present invention when seven electrodes are superimposed; FIG.15 is an exploded perspective view showing a general construction of the conventional flat type image display apparatus; and FIG.16 is a side view showing the conventional bonding method of the electrodes. It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. DESCRIPTION OF THE PREFERRED EMBODIMENT Hereafter, a preferred embodiment of the present invention is described with reference to the accompanying drawings. FIG.1 is an exploded perspective view showing a flat type image display apparatus 1. The image display apparatus 1 has a vacuum case constituted by a front panel 3, a rear panel 4 and a side wall part (not shown). A phosphor screen 2 is formed on an inner face of the front panel 3. An inbetween space defined by the front panel 3, the side wall part and the rear panel 4 is kept vacuum. A back electrode 5, plural linear cathodes 6 and a flat-shaped electrode unit 7 are provided from the back panel 4 toward the front panel 3. The linear cathodes 6 act as an electron beam source. The back electrode 5 is formed on an inner face of the back panel 4. The electrode unit 7 consists of an electron beam extracting electrode 7a, a modulation electrode 7b, a vertical focussing electrode 7c, a horizontal focussing electrode 7d, a horizontal deflection electrode 7e, a shield electrode 7f and a vertical deflection electrode 7g. These electrodes 7a --- 7g are disposed substantially in parallel with each other in a direction from the back panel 4 toward the front panel 3. Electron beams emitted from the linear cathode 6 pass through the electron beam extracting electrode 7a, the modulation electrode 7b, the vertical focussing electrode 7c, the horizontal focussing electrode 7d, the horizontal deflection electrode 7e, the shield electrode 7f and the vertical deflection electrode 7g, thereby getting focussed, modulated and deflected. Finally, a stream of the electron beams reaches a predetermined position on the phosphor screen 2, and thereby the screen emits light to make an image. FIG.2 is a plan view showing seven sheets of the electrodes 7a --- 7g which are piled up on a table (not shown) with a predetermined shift from each other in the horizontal direction (the widthwise direction in the figure). The horizontal direction implies a direction of the horizontal scanning with regard to the phosphor screen 2. The figure shows only one corner part of each of the electrodes 7a --- 7g. The electrodes 7a, 7b, 7c, 7d, 7e, 7f and 7g have identification holes 7aa, 7ba, 7ca, 7da, 7ea, 7fa and 7ga, respectively. Further, the electron beam extracting electrode 7a has a sight hole 7ab. The modulation electrode 7b has a pair of sight holes 7bb. The vertical focussing electrode 7c has a pair of sight holes 7cb. The horizontal focussing electrode 7d has a pair of sight holes 7db. The horizontal deflection electrode 7e has a pair of sight holes 7eb. The shield electrode 7f has a pair of sight holes 7fb. The horizontal deflection electrode 7g has a sight hole 7gb. Also, the electrodes 7a, 7b, 7c, 7d, 7e, 7f and 7g have temporary fixing parts 207a, 207b, 207c, 207d, 207e, 207f and 207g, respectively. In the figure, illustration of the configuration for passing electron beams through each of the electrodes 7a --- 7g is omitted for simplification of the drawing. FIG.3 is a plan view showing only the corner parts of the seven electrodes 7a --- 7g which are piled up on the table with a predetermined shift from each other in the vertical direction. The vertical direction implies a direction of the vertical scanning with regard to the phosphor screen 2. Each of the identification holes 7aa, 7ba, 7ca, 7da, 7ea, 7fa and 7ga and each of the sight holes 7ab, 7bb, 7cb, 7db, 7eb, 7fb and 7gb are formed in every corner of each of the electrodes 7a --- 7g in such manner that each identification hole and each sight hole make parallel translations toward the other three corners (right-lower, left-upper and left-lower corners) of each electrode. In one electrode (e.g., 7a), four identification holes (e.g., 7aa of four corners) are located to hold a predetermined relative positional relationship i.e., a horizontal interval and a vertical interval among them. This relative positional relationship is uniform with regard to all electrodes 7a --- 7g. As to a positional relationship of the identification holes 7aa --- 7ga among the electrodes 7a --- 7g, positions of the identification holes 7aa --- 7ga in the vertical direction coincide with each other, and their positions in the horizontal direction have a predetermined shift from each other. In this embodiment, the above-mentioned shift is uniformly 1 mm. Each of the identification holes 7aa --- 7ga is provided in a position included by a common area defined by six of the sight holes 7ab --- 7gb of other electrodes. For example, a position of the identification hole 7aa is in an area defined by the left-side sight holes 7bb, 7cb, 7db, 7eb and 7fb in FIG.3 and the sight hole 7gb at the time when the seven electrodes 7a --- 7g are piled up to complete the electrode unit 7 as shown in FIG.4. Also, position of the identification hole 7ba is in an area defined by the left-side sight holes 7cb, 7db, 7eb, 7fb and the sight holes 7gb, 7ab when the electrodes 7a --- 7g are piled up to complete the electrode unit 7. In a similar way to the above, the identification holes 7ca. 7da, 7ea and 7fa appear through the sight holes 7ab ---7gb (excluding 7cb), 7ab --- 7gb (excluding 7db), 7ab ---7gb (excluding 7eb) and 7ab --- 7gb (excluding 7fb), respectively. Thus, as shown in FIG.4, the respective identification holes 7aa --- 7ga are visible independently from each other. As a result, all the identification holes 7aa --- 7ga shown in FIG.4 are through-holes in the electronbeam traveling direction which is perpendicular to a sheet surface of FIG.4. By providing the electrodes 7a --- 7g with the sight holes 7ab --- 7gb each having the form elongated in the horizontal direction and corresponding to the identification holes 7aa --- 7ga, a total area in which the identification holes 7aa --- 7ga and the sight holes 7ab --- 7gb are aligned could be made smaller than a total area in which sight holes are formed independently from each other. In this embodiment, detection of the identification holes 7aa --- 7ga is carried out by means of an optical microscope. By making a uniform pitch between the adjacent two of the identification holes 7aa - -- 7ga, four sets of optical microscopes can be used as one unit microscope. Therefore, mechanically-originated deterioration in accuracy for the positioning is made minimum. Besides, since the identification holes 7aa ---7ga are of through-holes, an edge of each of the identification holes 7aa --- 7ga can surely be detected by a transmitted light which has passed through the identification holes 7aa --- 7ga. An accuracy in the position detection is thus improved. FIG.5 is a cross-sectional view showing the identification holes 7xa (x: a, b, ... , g). As shown in FIG.5, inner walls of the identification hole 7xa are formed into a conically bored shape, thereby to improve the accuracy in detecting a position of the identification hole 7xa. FIG.6 is a plan view showing a detail of the temporary fixing part 207x (x: a, b, ... , g) shown in FIG.2. This figure (FIG.6) shows one typical configuration. In FIG.2, although illustration is limited to one (right-upper corner) of four corners of the electrodes 7a --- 7g, the temporary fixing parts 207a ---207g are provided in the other three corners of each of the electrodes 7a --- 7g. The configuration of the temporary fixing parts 207a --- 207g is also provided in the right-lower corner of the electrodes 7a --- 7g in a manner that the configuration of the temporary fixing parts 207a --- 207g makes parallel translations toward the right-lower corner of the electrodes 7a --- 7g, respectively. The configuration of the temporary fixing parts in the left half of the electrodes 7a --- 7g is symmetric with respect to a vertical (lengthwise direction in FIG.2) centerline (not shown) of each of the electrodes 7a --- 7g. Positional relationship between the right and left temporary fixing parts may be shifted by a certain value in the vertical (lengthwise in the figure) direction. In FIG.6, the temporary fixing part 207x is disposed inside the electrode 7x. The temporary fixing part 207x has a fixing portion 207xb and an elastic portion 207xa. Although these portions 207xa and 207xb are members of the electrode 7x at this stage, they (207xa, 207xb) are removed after completion of the permanent bonding as described later. The electrode 7x has slanted edges 407x at a base portion 71x of the elastic portion 207xa. A chain line 307x shows a cut-off line of the temporary fixing part 207x which is to be removed from the electrode 7x. When the temporary fixing part 207x was removed from the electrode 7x at the line 307x, existence of the slanted edges 407x is significant in a standpoint that only obtuse angle edges are left in the base portion 71x of the electrode 7x. If an acute angle edge were left, there would arise a problem that an electric discharge occurs when a high voltage is applied to the phosphor screen 2 (FIG.1). Next, a method for bonding the electrode unit 7 will be described. As shown in FIG.1, the electrode unit 7 is made by bonding respective electrodes 7a --- 7g to each other with the respective predetermined intervals secured therebetween, while the electrical insulation is kept from each other. As an example, a method for bonding the shield electrode 7f and the vertical deflection electrode 7g will be described hereinafter with reference to FIGs.7, 8, 9 and 10. FIG.7 is a side view showing a bonding process of the shield electrode 7f and the vertical deflection electrode 7g with an electrode bonding tool (9, 10). FIG.8 is a perspective view showing a main part including the temporary fixing parts 207f and 207g. FIG.9 and FIG.10 are side views seen from "A" in FIG.8 before and after the bonding process, respectively. In FIG.7, the shield electrode 7f and the vertical deflection electrode 7g are insulated from and bonded with each other by an insulative bonding material 8. This insulative bonding material 8 includes a bonding glass member 8a and a spacer glass member 8b for making a predetermined gap between the electrodes 7f and 7g. The spacer glass member 8b is put between a pair of bonding glass members 8a. A substrate 9 and a stamper 10 constitute the aforementioned electrode bonding tool by a baking process. A metal sheet 12a for mainly protecting the vertical deflection electrode 7g is provided between the substrate 9 and the vertical deflection electrode 7g, and a metal sheet 12b for mainly protecting the shield electrode 7f is provided between the stamper 10 and the shield electrode 7f. First, in FIG.7, the metal sheet 12a and the vertical deflection electrode 7g are mounted on the substrate 9. The insulative bonding materials 8 are put on predetermined positions on the vertical deflection electrode 7g. Next, in FIG.8, a temporary fixing spacer 507 is put on the fixing portion 207gb of the temporary fixing part 207g, and the shield electrode 7f is mounted on the insulative bonding materials 8. In this state, four identification holes 7fa formed in respective corners of the shield electrode 7f can be detected by the four optical microscopes, respectively. Also, four identification holes 7ga (FIG.3) formed in respective corners of the vertical deflection electrode 7g can be detected. To make an optimum positional relationship between the identification holes 7ga and 7fa, position of at least one of the electrodes 7g and 7f is corrected in compliance with calculation results for minimizing a deviation of each interval between the identification holes 7ga and 7fa. After completion of the above-mentioned position correction, the fixing portion 207fb of the shield electrode 7f and the fixing portion 207gb of the vertical deflection electrode 7g are bonded with each other as shown in FIG.9 via the temporary fixing spacer 507 by means of a known bonding method such as spot welding. In FIG.9, a thickness t s [µm] of the temporary fixing spacer 507 has the following relation: t 8b - 50 ≦ t s ≦ t 8a + 50 wherein t 8a represents a thickness of the bonding glass member 8a before the melting process, and t 8b represents a thickness of the spacer glass member 8b. Further, inventors empirically confirmed that the following relation is desirable: t 8b - 25 ≦ t s ≦ (t 8a - t 8b )/2. Next, in FIG.7, the protection metal sheet 12b is mounted on the shield electrode 7f, and the stamper 10 is put on the protection metal sheet 12b, thereby constituting a baking assembly 701. This baking assembly 701 is heated in an oven (not shown) at the temperature of 450 to 500°C. The bonding glass members 8a are thereby melted and crystallized. By the crystallization, the bonding glass members 8a keep a tight bonding state even when they are heated again up to the melting temperature at the subsequent steps. Thus, the shield electrode 7f and the vertical deflection electrode 7g are tightly bonded with each other as shown in FIG.10. After completion of the above-mentioned "permanent" bonding process, the fixing portions 207fb, 207gb and the elastic portions 207fa, 207gb are removed at the respective cut-off lines 307f and 307g from the electrodes 7f and 7g, respectively. Thus, insulative bonding process of the electrodes 7f and 7g is completed. As is apparent from FIGs.9 and 10, a total thickness t1 before the permanent bonding process decreases to a thickness t2 after the permanent bonding process. The elastic portions 207fa and 207ga of the respective temporary fixing parts 207f and 207g follow this change in thickness to restore the bend of themselves, thereby preventing a positional deviation between the electrodes 7f and 7g which may be caused by the melting process. In a similar way to the above, the horizontal focussing electrode 7d and the horizontal deflection electrode 7e are bonded to each other, keeping the insulation therebetween. Also, the modulation electrode 7b and the vertical focussing electrode 7c are bonded to each other, keeping the insulation therebetween. Finally, three units, whose bonding processes have been completed, and the electron beam extracting electrode 7a are bonded with and insulated from each other via the insulative bonding materials 8. The electrode unit 7 is thus completed. Hereupon, FIG.11 is a cross-sectional view showing seven electrodes 7a --- 7g taken on line XI-XI in FIG.4. Chain lines represent light beams with which the electrodes 7a --- 7g are irradiated from the side of the electrode 7a or 7g. As is apparent from FIGs.4 and 11, a width of each of the sight holes 7ab, 7bb, 7cb, 7db, 7fb and 7gb is larger than a diameter of the identification hole 7ea. The diameters of six sight holes 7ab, 7bb, 7cb, 7db, 7fb and 7gb are equal to each other. The diameter is of a size which allow the light beams to pass therethrough when the identification hole is located in the end electrode (i.e., the electrode 7a or 7g) of the electrode unit. Next, another configuration of the identification hole 7xa and the sight holes 7xb will be described. FIG.12 is a cross-sectional view showing another configuration of the identification hole 7ea and the sight holes 7ab, 7bb, 7cb, 7db, 7fb and 7gb. As is apparent from comparison with FIG.11, the more the sight hole 7ab, 7bb, 7cb, 7db, 7fb or 7gb is away from the identification hole 7ea, the larger a width of the sight hole 7ab, 7bb, 7cb, 7db, 7fb or 7gb becomes. Therefore, light beams represented by chain lines pass through only a minimum space defined by edges of the sight holes 7ab, 7bb, 7cb, 7db, 7fb, 7gb and the hole 7ea. To partially or wholly realize the above-mentioned configuration shown in FIG.12, a configuration of the electrode unit 7 in a plan view can be formed as shown in FIG.13 or FIG.14. According to the configuration of FIG.13 or FIG.14, a cut-off area of the electrode for making the sight hole is made smaller than that of the configuration shown in FIG.4. Therefore, it is avoidable to undesirably weaken a mechanical strength of the electrode in its peripheral part. Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting.

Claims: A method of fabricating an electrode unit (7) which is used in a flat type image display apparatus and consists of a plurality of flat-sheet-shaped electrodes, said method comprising the steps of: mounting in position a first electrode (e.g., 7f) on a second electrode (e.g., 7g) via an insulative bonding material (8), each of said first and second electrode having a temporary fixing part (207x) comprising a fixing portion (207xb) and an elastic portion (207xa); temporarily fixing said first electrode (7f) to said second electrode (7g) via a pair of opposing fixing portions with one fixing portion being formed in said first electrode (7f) and the other fixing portion in said second electrode (7g) and with the elastic portions corresponding to said opposing fixing portions being bent towards each other; permanently fixing said first electrode (7f) to said second electrode (7g) via said insulative bonding material (8); and removing said temporary fixing parts (207f, 207g). A method for fabricating an electrode unit (7) in accordance with claim 1, wherein said step of temporarily fixing is executed via a temporary fixing spacer (507) between said temporary fixing parts (207f, 207g), and said temporary fixing spacer (507) has a predetermined thickness.

Inventors: IMAI KANJI, INADA MAKOTO, NAKATANI TOSHIFUMI, SEKIGUCHI TOMOHIRO, IMAI, KANJI, INADA, MAKOTO, NAKATANI, TOSHIFUMI, SEKIGUCHI,TOMOHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: H01J9
IPC codes: H01J31, H01J9, H01J29